1. Field of the Invention
The present invention relates to a powder conveying device, a process cartridge including the powder conveying device, and an image forming apparatus.
2. Description of the Related Art
In recent years, demand has arisen for miniaturizing image forming apparatuses such as a printer, a copying machine, a facsimile machine. As a result of miniaturizing the image forming apparatuses, a powder conveying path having a tubular body cannot be linearly disposed in the powder conveying device while avoiding other members therein, where the powder conveying path serves as a path conveying a toner from a toner accommodating container to a developing device therein; and a path conveying a waste toner collected from a cleaning unit to a waste toner-accommodating container therein. Thus, it is disposed so as to be curved therein, and a generally usable powder conveying device is a powder conveying device configured to dispose a conveying screw capable of being curved in the inner part of the tubular body.
The conveying screw includes a rotation axis portion and a blade portion, where the blade portion is helically formed on an outer periphery of the rotation axis portion. The conveying screw is disposed in the powder conveying path having a curved portion, and thus the toner and the waste toner can be conveyed even in the curved powder conveying path.
For example, as shown in Japanese Patent Application Laid-Open (JP-A) No. 2008-268445, proposed is a low-cost powder conveying device, where the powder conveying device include a resin material capable of curving and having flexibility as a material of the conveying screw; and is formed by integrating a rotation axis portion with a blade portion.
However, in cases where the conveying screw is used, the below-described problems may be caused.
In the curved powder conveying path, the conveying screw containing the resin material is left to stand for a long time in a state that it is not operated, and thus peculiarity following a shape of the curved powder conveying path occurs in the conveying screw, as property of the resin materials.
In particular, in cases where the conveying screw is left to stand in an environment of high temperature, a degree of this peculiarity comes more significantly. In this state, the conveying screw is rotated by transferring driving power, and thus a portion having a peculiarity temporarily causes rotary malfunction in the powder conveying path. As a result, when rotary torque of the conveying screw is fluctuated and the conveying screw is rotated, collision with an inner wall of the powder conveying path occurs in a portion having a peculiarity.
Thus, an extraordinary noise is caused by colliding the conveying screw with the inner wall of the powder conveying path, which is problematic when users have received the products. It is believed that the louder the noise generated during driving is, the more severely the conveying screw collides with the inner wall of the powder conveying path. In cases where a driving part of the conveying screw is connected with a row of photoconductor drives, banding is caused because the rotary torque is fluctuated and the vibration is caused by colliding the conveying screw with the inner wall of the powder conveying path, which is a factor in forming an abnormal image.